private async Task ReadStringValueAsync()

in src/Elastic.Apm/Libraries/Newtonsoft.Json/JsonTextReader.Async.cs [1168:1302]
123 lines of code
50 McCabe index (conditional complexity)

        private async Task<object?> ReadStringValueAsync(ReadType readType, CancellationToken cancellationToken)
        {
            EnsureBuffer();
            MiscellaneousUtils.Assert(CharBuffer != null);

            switch (_currentState)
            {
                case State.PostValue:
                    if (await ParsePostValueAsync(true, cancellationToken).ConfigureAwait(false))
                    {
                        return null;
                    }
                    goto case State.Start;
                case State.Start:
                case State.Property:
                case State.Array:
                case State.ArrayStart:
                case State.Constructor:
                case State.ConstructorStart:
                    while (true)
                    {
                        char currentChar = CharBuffer[CharPos];

                        switch (currentChar)
                        {
                            case '\0':
                                if (await ReadNullCharAsync(cancellationToken).ConfigureAwait(false))
                                {
                                    SetToken(JsonToken.None, null, false);
                                    return null;
                                }

                                break;
                            case '"':
                            case '\'':
                                await ParseStringAsync(currentChar, readType, cancellationToken).ConfigureAwait(false);
                                return FinishReadQuotedStringValue(readType);
                            case '-':
                                if (await EnsureCharsAsync(1, true, cancellationToken).ConfigureAwait(false) && CharBuffer[CharPos + 1] == 'I')
                                {
                                    return ParseNumberNegativeInfinity(readType);
                                }
                                else
                                {
                                    await ParseNumberAsync(readType, cancellationToken).ConfigureAwait(false);
                                    return Value;
                                }
                            case '.':
                            case '0':
                            case '1':
                            case '2':
                            case '3':
                            case '4':
                            case '5':
                            case '6':
                            case '7':
                            case '8':
                            case '9':
                                if (readType != ReadType.ReadAsString)
                                {
                                    CharPos++;
                                    throw CreateUnexpectedCharacterException(currentChar);
                                }

                                await ParseNumberAsync(ReadType.ReadAsString, cancellationToken).ConfigureAwait(false);
                                return Value;
                            case 't':
                            case 'f':
                                if (readType != ReadType.ReadAsString)
                                {
                                    CharPos++;
                                    throw CreateUnexpectedCharacterException(currentChar);
                                }

                                string expected = currentChar == 't' ? JsonConvert.True : JsonConvert.False;
                                if (!await MatchValueWithTrailingSeparatorAsync(expected, cancellationToken).ConfigureAwait(false))
                                {
                                    throw CreateUnexpectedCharacterException(CharBuffer[CharPos]);
                                }

                                SetToken(JsonToken.String, expected);
                                return expected;
                            case 'I':
                                return await ParseNumberPositiveInfinityAsync(readType, cancellationToken).ConfigureAwait(false);
                            case 'N':
                                return await ParseNumberNaNAsync(readType, cancellationToken).ConfigureAwait(false);
                            case 'n':
                                await HandleNullAsync(cancellationToken).ConfigureAwait(false);
                                return null;
                            case '/':
                                await ParseCommentAsync(false, cancellationToken).ConfigureAwait(false);
                                break;
                            case ',':
                                ProcessValueComma();
                                break;
                            case ']':
                                CharPos++;
                                if (_currentState == State.Array || _currentState == State.ArrayStart || _currentState == State.PostValue)
                                {
                                    SetToken(JsonToken.EndArray);
                                    return null;
                                }

                                throw CreateUnexpectedCharacterException(currentChar);
                            case StringUtils.CarriageReturn:
                                await ProcessCarriageReturnAsync(false, cancellationToken).ConfigureAwait(false);
                                break;
                            case StringUtils.LineFeed:
                                ProcessLineFeed();
                                break;
                            case ' ':
                            case StringUtils.Tab:

                                // eat
                                CharPos++;
                                break;
                            default:
                                CharPos++;

                                if (!char.IsWhiteSpace(currentChar))
                                {
                                    throw CreateUnexpectedCharacterException(currentChar);
                                }

                                // eat
                                break;
                        }
                    }
                case State.Finished:
                    await ReadFinishedAsync(cancellationToken).ConfigureAwait(false);
                    return null;
                default:
                    throw JsonReaderException.Create(this, "Unexpected state: {0}.".FormatWith(CultureInfo.InvariantCulture, CurrentState));
            }
        }